Methionine sulfoxide reductases (Msr's) catalyze the reduction of methionine sulfoxide back to (normal) methionine. The result is reactivation of oxidatively damaged proteins and this activity is known to facilitate successful gastric colonization by H. pylori. This focused project is designed to identify the critical amino acid residues associated with one identified H. pylori protein (catalase) that undergoes this reductive repair process. Identification of the specific Met residues repaired by Msr is of the most immediate interest. The residues will be identified by studying pure H. pylori Msr and its interaction with pure catalase. The information from the pure protein studies will be used to assess the degree of oxidative Met residue damage the target protein sustains upon stress agent exposure of whole cells. The proposed project is a small self-contained one on a highly successful pathogen. PUBLIC HEALTH RELEVANCE: The repair of an amino acid (methionine) by a bacterium that causes peptic ulcers and gastric cancers is important for the pathogens survival in the host. It is proposed to understand what factors influence the need for this repair in a key protein. [unreadable] [unreadable] [unreadable] [unreadable]